The in-situ generation of hydrogen peroxide in the electro-Fenton process is paramount. For this reason, in this research the electrocatalytic activity of three carbon materials was evaluated in the reaction of oxygen reduction via two electrons. Furthermore, in order to eliminate the use of iron salts in solution (homogeneous process), the iron was electrodeposited on the surface of the carbon material and was applied in a heterogeneous electro-Fenton process for the degradation of methyl orange dye. The largest amount of generated H ₂ O ₂ was achieved with the Carbon Felt (CF) electrode (460 mg L ⁻¹ ) without iron after 60 minutes. The electrodes with electrodeposited iron were characterized by SEM and EDS, which showed that the surface of the Carbon Sponge (CS) electrode had the largest amount of iron (23.84 %). However, the CF electrode showed a greater and faster degradation of the dye (98 %) after 30 minutes of treatment. The CF material was the best and most-viable choice of material compared to the CS and Carbon Cloth (CC) for industrial application in electro-Fenton processes, due to its greater catalytic activity in the production of H ₂ O ₂ , uniform distribution of iron, more efficient TOC removal and lower cost per cm ² of material.